1. Field of the Invention
The invention relates to polyether polyols made by alkoxylating polyfunctional initiators and more particularly relates to polyether polyols made from alkoxylating a mixture of partially alkoxylated initiators having different numbers of active hydrogens which was modified with epoxy resins.
2. Other Polyols in the Field
Presently, polyether polyols suitable for use in flexible foams are made by the reaction of trifunctional initiators such as glycerine with mixtures of alkylene oxides. Persons skilled in the art of making polyols can add alkylene oxides to polyhydric initiators such as glycerine or to an intermediate molecular weight alkylene oxide adduct of the initiator to prepare products in the 40-60 hydroxyl number range. For examples of polyols made by this technique, see U.S. Pat. Nos. 3,393,243; 3,535,307; 3,706,714; 3,847,992; 4,166,172 and 4,316,991.
While generally satisfactory, foam prepared from the prior art polyols are not firm enough for many cushioning applications, particularly at lower foam densities. Conventional means of producing firmer (higher ILD) foams such as higher functionality initiators, short chain crosslinkers or fillers lead to other deficiencies in foam properties such as closed cells, poor tear and elongation properties and increased foam density. It is, therefore, an object of this invention to increase the functionality of triols and the like by mixing in a minor portion of a higher functionality polyol initiator and modifying the mixture with epoxy resins. Several patents describe mixtures of initiators used to prepare polyols for polyurethane foams. Almost all are concerned with the preparation of polyols for rigid urethane foams. Usually, these processes involve sucrose with water, glycols, glycerine, etc. The use of lower functional polyols permit one to make polyols for rigid urethane foams that are easier to handle and the resulting rigid foams have much finer cells.
A recent example is U.S. Pat. No. 4,380,502 which employs 80 to 20 wt.% of formitol (a mixture of polyhydric alcohols having an average hydroxyl functionality of at least 3) and 20 to 80 wt.% of sucrose. The introductory section of this patent is a good summary of the art of mixed initiators and is incorporated by reference herein.
Also of interest is Japanese Kokai Tokkyo Koho JP 57,174,313 (82,174,313), see Chemical Abstracts 98: 144401c (1983). This disclosure describes urethane foams having good post formability by hot pressing which are prepared from reacting polyisocyanates and polyol mixtures. The polyol mixtures are 30 to 90 parts of polyether polyols derived from a 10 to 40:60 to 90 molar mixture of sucrose and glycerol, respectively, and alkylene oxides having a molecular weight between 4000 and 10,000, and 10 to 70 parts of polyether diols and/or triols having an average hydroxyl number between 50 and 300. Apparently, sucrose and glycerol are first mixed and then the alkylene oxides are reacted therewith (for example, a 90:10 propylene oxide/ethylene oxide mixture) before a polyether diol is added thereto to give the polyol component for the foams described therein. This method is quite different from the invention herein, particularly with regard to when the various alkoxylations take place.
Other patents disclose reactions involving polyols and epoxy resins. Japanese Pat. No. 71-24,255 concerns the reaction of a glycerine-based 3,000 molecular weight triol with 2% bisphenol A epoxy resin to produce foams with increased hardness. A close examination of this patent will show that the epoxy resin is added at only the end of the triol chain. Where the epoxy resin is added in the polyol chain will make a substantial difference in how the modified polyol performs in producing open-celled flexible foams with improved load bearing properties.
U.S. Pat. No. 3,012,984 describes how hydroxyl terminated polyesters, epoxy resins and isocyanate terminated prepolymers may be reacted in an inert organic solvent to produce metal primers and coatings. U.S. Pat. No. 3,010,940 discloses how phenol, epoxy resins, polyisocyanates and alphamethylbenzyldimethylamine react to produce various polyurethane coatings.
U.S. Pat. No. 3,448,046 describes how polyols containing chlorine are mixed with epoxy resins before reaction with an isocyanate. The free epoxides scavenge the HCl in the polyol and do not contribute to the functionality of the polyol. The reaction of an epoxide with an alcoholic hydroxyl group is set out in U.S. Pat. No. 3,317,609. Further, British Pat. No. 968,102 describes how polyols suitable for polyurethane foams may be prepared from the reaction of a polyol and an epoxy resin in the presence of an acidic catalyst.
Further prior art polyols include those described in German Offenlegungschrifft No. 2,056,080. This patent describes how epoxy adhesives may be made by the reaction of epoxy resins with 4-mercaptobutanol-blocked urethane prepolymers which are made from toluene diisocyanate and various polyols. German Offenlegungschrifft No. 1,905,696 discloses how polyurethane latices may be produced by chain extending a urethane prepolymer by using the reaction product of polyethylene glycols of a molecular weight of about 5,000 to 10,000 and an aromatic diglycidyl ether. The modification of epoxy resins by heating them with added polyalkoxylated disaccharides is described in Belgium Pat. No. 785,020.
Also of particular interest is U.S. Pat. No. 4,316,991 to Speranza, et al. which describes the modification of polyether polyols by their reaction with epoxy resins and alkylene oxides such that the epoxy resin is positioned internally in the resulting modified polyol, as well as the reference cited in the prosecution therein. U.S. Pat. No. 4,309,532 concerns the modification of rigid amino polyols by their reaction with epoxy resins and alkylene oxides, while U.S. Pat. No. 4,323,658 details a method of preparing polyether polyols in the 200 to 1,000 molecular weight range by modifying a polyol initiator with an epoxy resin and one or more alkylene oxides.